[Year 12 SofDev] Resource flows in a DFD

Tue Apr 15 10:59:45 EST 2008

I agree, and I guess that is where theory merges with the realities of the
real world. You have also alluded in other emails to the fact that there are
often no exact definition of some areas such as the SDLC for example, so I
think some of these concepts need to be explained to students not as the one
and only explanation but as one possible solution.

I still believe that DFD's should not contain physical resources in them
because then by definition it isn't a DFD, but that's just my opinion, but I
do understand the difficulties and frustrations when opening up books and
finding a variety of explanations for the one concept.

Kind regards

Allan Barnes, CEO
Australian Institute of Education and Training
P.O. Box 171
Brunswick West 3055
Ph: (03) 9387 2051
FAX: (03) 9387 3470
Mobile: 0409 428 221

-----Original Message-----
From: sofdev-bounces at edulists.com.au [mailto:sofdev-bounces at edulists.com.au]
On Behalf Of Mark Kelly
Sent: Tuesday, 15 April 2008 10:45 AM
To: Year 12 Software Development Teachers' Mailing List
Subject: Re: [Year 12 SofDev] Resource flows in a DFD

Hi Allan.  Yes, I realise DFDs have usually only shown data flows, as 
their name implies.  My concern was my research has found that physical 
resource flows (such as real books) have been included in context 
diagrams and DFDs.  That's the sticking point.

Allan Barnes wrote:
> My understanding from Uni days is that DFD's are diagrams of logical
systems
> and represent flow of information. I don't quite follow what you mean when
> you say a resource flow, Mark, but the DFD can in my opinion show things
> such as book orders, for example, as this is a flow of information,
however,
> it would not show that it is Michael who has ordered the books, or that he
> has ordered it over the phone, etc.
> 
> The physical design provides information about how the processing takes
> place. It may show who sends or receives the information, who manipulates
> the data, where it is manipulated, what happens to it, what structure it
> takes, whether the transaction occurs on the computer, the Internet, by
> telephone, by cash register or by a paper-based method. The physical
design
> will also include details about the specifications of the hardware and
> software that is to be used in the information system. It uses diagrams
such
> as hierarchy charts, structure charts and system flow charts to represent
> the information.
> 
> 
> 
>  
> 
> Kind regards
>  
> Allan Barnes, CEO
> Australian Institute of Education and Training
> P.O. Box 171
> Brunswick West 3055
> Ph: (03) 9387 2051
> FAX: (03) 9387 3470
> Mobile: 0409 428 221
>  
> -----Original Message-----
> From: sofdev-bounces at edulists.com.au
[mailto:sofdev-bounces at edulists.com.au]
> On Behalf Of Kevin Feely
> Sent: Monday, 14 April 2008 4:49 PM
> To: Year 12 Software Development Teachers' Mailing List
> Subject: Re: [Year 12 SofDev] Resource flows in a DFD
> 
> Hi mark,
> In all of the exercises i have done with context diagrams (level 0) and 
> DFD's (mainly level 1 and only discussion about level 2) i have always 
> said only data (information) should be represented. That the DFD is not 
> concerned with the actual goods ordered or purchased for example, but 
> the information these transactions generate.
> I suppose this is because we are modeling information systems using the 
> DFD tool.
> I suppose it is possible to model physical systems with the DFD as well 
> ( obviously from your link!) but  iam not sure they should be intertwined.
> That is if a student represents a physical transaction on my information 
> DFD i would regard that as an error.
> regards
> Kev
> 
> Mark Kelly wrote:
>> I can't remember seeing a resource flow in an SD DFD, but apparently 
>> they exist (e.g. 
>> http://www.getahead-direct.com/gwba03-context-diagram.htm)
>>
>> Are they deliberately avoided in SD or are they not industry-standard?
>>
>> Cheers
>> Mark
>>
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-- 
Mark Kelly
Manager - Information Systems
McKinnon Secondary College
kel AT mckinnonsc.vic.edu.au
McKinnon Rd, McKinnon 3204, Victoria, Australia
Direct line / Voicemail: 8520 9085 Fax +613 9578 9253

Webmaster - http://www.mckinnonsc.vic.edu.au
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